NPE with listbox and listgroup with @ZKController

[GoogleCodeExporter]

What steps will reproduce the problem?
piece of ZUL:
<listbox id="deviceList" width="100%" checkmark="true"
    vflex="true" apply="${deviceMenuCtl.deviceListCtl}"
    selectedItem="@{deviceMenuCtl.selectedXmodData}"
    emptyMessage="${labels.menu.deviceList.emptyMessage}">
    <listhead sizable="true">
        <listheader id="supplier"
            label="${labels.supplier}" sort="db()" />
        <listheader id="model" label="${labels.model}"
            sort="db()" />
        <listheader id="protocol"
            label="${labels.protocol.$}" sort="db()" />
    </listhead>
        <listgroup label="test" />
    <listitem self="@{each=device}">
        <listcell label="@{device.supplier}" />
        <listcell label="@{device.model}" />
        <listcell label="@{device.protocol}" />
    </listitem>
</listbox>
<dlpaging apply="${deviceMenuCtl.deviceListCtl}"
    pageSize="15" /> 

piece of code:
// Controller per popolare l'accordion del menu dei device
@ZkController
DLListboxController<XmodData> deviceListCtl = new 
DLListboxCriteriaController<XmodData>(
        "DeviceList") {
    @Override
    protected DLResponse<XmodData> loadData(DLSearch<XmodData> search) {
        logger.debug("Ricerca dati xmod nel db");
        return xmodDataDAO.searchAndCount(search);
    }
};

What is the expected output? What do you see instead?
>>java.lang.NullPointerException
>>  at 
org.zkoss.zk.ui.AbstractComponent.checkParentChild(AbstractComponent.java:1064)
>>  at 
org.zkoss.zk.ui.AbstractComponent.insertBefore(AbstractComponent.java:1084)
>>  at org.zkoss.zk.ui.AbstractComponent.appendChild(AbstractComponent.java:1242)
>>  at 
cz.datalite.zk.components.list.controller.impl.DLListboxComponentControllerImpl.
fireOrderChanges(DLListboxComponentControllerImpl.java:225)
>>  at 
cz.datalite.zk.components.list.DLListboxGeneralController.onCreate(DLListboxGene
ralController.java:155)
>>  at 
cz.datalite.zk.components.list.controller.impl.DLListboxComponentControllerImpl.
onCreate(DLListboxComponentControllerImpl.java:160)
>>  at cz.datalite.zk.components.list.view.DLListbox.onCreate(DLListbox.java:31)

What version of the product are you using? On what operating system?
ZK 5.0.7.1
ZK-DL 1.1
Windows 7 x64
Jetty 7.5.1
JDK 1.6.0_27

Please provide any additional information below.

Original issue reported on code.google.com by [email protected] on 30 Sep 2011 at 9:31

[GoogleCodeExporter]

I think that the problem is that Listgroup implements Listitem, and in 
DLListboxComponentControllerImpl:244 you do:
renderTemplate = listbox.getItemAtIndex( 0 );
assuming the first item in a Listbox is a <listitem>, but in my case the first 
item is a <listgroup>. The fact that even Listgroup (as a class) is a Listitem 
generates this problem and even the other is issue 2 I created.

Original comment by [email protected] on 30 Sep 2011 at 9:55

[GoogleCodeExporter]

Hello, I'm afraid that we do not support listgroups yet, but we will have a 
look and let you know soon.

Original comment by [email protected] on 7 Nov 2011 at 12:21